The inflammatory response is critical in regulating a broad spectrum of physiologic and pathologic states. The tissue macrophage is a central regulator of this response - from initiation to resolution o inflammation. Recent studies have identified Hypoxia-inducible Factor 1alpha(HlF-1 alpha) as a key regulator of macrophage activation function. Using a combination of gain- and loss-of-function approaches, the PI has identified KLF2 as a novel endogenous regulator of HlF-1 alpha expression and function. Specifically, our studies show that (1) KLF2 inhibits HlF-1 expression and transcriptional activity; (2) altering KLF2 expression affects HIF-lalpha target gene expression, ATP production, cytokine/MMP expression, and bacterial/tumoricidal activity of macrophages. In this proposal a cornbination of molecular and genetic approaches will be undertaken (1) to determine the molecular basis for KLF2-mediated inhibition of HIF-lalpha expression, (2) to evaluate the effect of altering KLF2 levels on hypoxia or LPS mediated activation of macrophages, and (3) to assess the effect of altering KLF2 levels on hypoxia or LPS-mediated macrophage function in vivo. These studies will provide the foundation for the applicant to achieve his longterm goals of translating basic mechanisms of inflammation toward the development of novel therapies. Continuing support of this project via a ROO award would play a pivotal and requisite role in the Pi's development into an independent investigator. The Pl has completed requisite additional training during the K99 phase of award and is now transiting toward becoming an NIH-funded independent investigator with adequate institutional support.